In known solutions, the coupling between two tubular or box-like structural elements is obtained by making complementary projections and recesses on end portions of tubular structural elements which are interlocked, as shown, for example, in document U.S. Pat. No. 5,403,043. However, this type of solutions has the disadvantage of providing poor modularity, thus limiting the coupling configurations allowed to only substantially rectilinear joints.
Solutions of joint to be interposed between two or more tubular structural elements and comprising joint branches variously oriented in space and each suitable for being inserted in a tubular structural element, are also known. This type of joints allows modular framework structures to be formed. Known types of joints generally comprise joint branches suitable for being inserted with interference into the longitudinal cavities of the tubular structural elements so as to form a frictional fit.
This type of solution requires the application of an increased pressure for inserting the joint branch with interference into the longitudinal cavity of the tubular structural element. Therefore, only using joints of this type is disadvantageous when making a modular frame because the force to be applied for driving in a joint may create stresses and deformations in an already assembled portion of frame and at the same time, be laborious and not comfortable. Moreover, this type of coupling is unsuitable for successive assembling and disassembling because it wears out quickly.
Moreover, joints are known comprising locking keys in which a joint branch is provided with a key comprising cantilevered extensions, which key is inserted in a housing made in the walls of the longitudinal cavity of the tubular structural element, and in which said key, by rotating about the longitudinal axis thereof, is coupled with the cantilevered extensions thereof against surfaces of the housing, which conveniently are arranged undercut.
A solution of this type is disclosed for example, in document US-2010-014912. Although it is advantageous, such a solution has certain drawbacks because it makes difficult the related positioning of the tubular element and of the key, and indeed such a solution imposes the provision of an increased number of components. A similar solution is disclosed for example, in document US-2006-0278139, which shows a joint solution obtained on structural elements which with the truncated-conical surfaces thereof form a fit which promotes the related positioning of structural elements. Although it is partially advantageous, such a solution in any case has certain difficulties associated with making accurate conical abutment planes.
Further examples of joints comprising locking keys are known from DE-102005028573, US-2008-072515, WO-2013-187020 and U.S. Pat. No. 3,966,340.
The need is therefore felt to devise a solution for the drawbacks of the prior art mentioned hereto.
The need is felt to provide a solution of joint which is suitable for forming a joint, which can be reversed, coupled and disengaged in a simple manner while avoiding to provide fastening elements such as e.g., screws, and at the same time avoiding to use assembly tools while providing a certain positioning of the different elements of the joint.